cannot completely empty trash in Mojave

The situation is clear for me. 

It seems that you deleted profile data for some user accounts manually (not by user & group management).

Some Mail.app settings in those profiles was locked by system.

You tried fix it by:

Deleting your user account Trash folder:

rm -rf ~/.Trash/*

Resetting the filesystem permissions:

cd ~/.Trash

chflags -R nouchg *

Deleting trash with privileged system access.

sudo rm -rf ~/.Trash/*

Using enabled root account, tried to delete all users accounts Trashes folders.

sudo rm -rf ~/.Trash/*

Keep calm we are close, 3 reboots left. :)

DataVaults are folders to which neither the user nor third-party software has any access at all. The only software which can see and work with their contents are certain Apple-signed products which have a specific entitlement to do so.

At this time, the only other method to acquire access to the directory is to turn off SIP (About System Integrity Protection on your Mac - Apple Support)

Reboot your computer into Recovery Mode by holding down Command + R on startup

Open Terminal from the Utilities menu

Run command:

csrutil disable

Reboot your computer

Login

Open Terminal from the Utilities menu

Run command:

sudo rm -rf ~/.Trash/* 

Reboot your computer into Recovery Mode by holding down Command + R on startup

Open Terminal from the Utilities menu

Run command:

csrutil enable

before using root account you could also try to

sudo rm -rf /users/*/.Trash

How to enable the root user on your Mac or change your root password - Apple Support

Please login as root, and try to empty folder in normal way if any files in it, if not,

please always be careful with rm. (this command will remove .Trash of any user in system)

 rm -rf /users/*/.Trash

Don't forget to disable root account after.

Sticky moments, I was having a similar problem with a "folder from ****", as we used to call them, since this past December. I tried all of the usual Terminal tricks -- as mentioned by ⁤aaplCore -- but nothing seemed to work. Whenever I tried to empty the trash, I would get the same message as you stating that the folder was in use.

I recall reading some time ago that this problem sometimes results from a file or folder becoming orphaned from something else that it was once related to. One thing I do know is that this problem has existed on macOS for many years, and there just seems to be no solution for some of us, other than taking very drastic measures.

But then something occurred to me. I do twice daily backups of my entire internal hard drive to an external hard drive.

So, while booted into my internal drive, I opened the desktop icon for my external drive, found the same troublesome folder, and I was able to delete it without a problem.

So, then I thought to myself, "If I boot my machine from my external backup drive, maybe I can do things in reverse."

In other words, maybe I could open the desktop icon for my internal drive, find the troublesome folder, and delete it that way.

So, that is what I did. I booted my iMac from my external drive. But guess what? When I tried to delete that untrashable folder on the internal hard drive, I got the very same error. That is, that it was in use, and couldn't be deleted.

But here's the weird part. Once I booted back into my internal hard drive, the troublesome folder was gone. I think I may have tried to empty the trash once I was booted back into my internal drive. I can't remember now.

But the point is, I finally got rid of that stubborn folder.

I don't know if you have a bootable backup drive, but if you do, you might want to give my technique a shot. It may possibly work for you.

aaplCore, thanks for your perseverance. Disabling SIP allowed me to delete .Trash, so now I've got new respect for that tech. Thanks for digging in and diagnosing what's going on with the protected folders and the DataVaults item.

Make sure you re-enable SIP.

Launch Terminal and then proceed:

cd ~/.Trash

chflags -R nouchg *

Try to empty Trash as usual. If it doesn't works, try run

sudo rm -rf ~/.Trash/*

Have a nice time with your mac!

You are welcome. Glad to hear that aaplCore helped you to resolve your issue. :)

I did exactly the same thing, thank you for the solution applCore !!!

Glad to read it.

Thanks for using Communities.

Yup, rebooted into my user account and did that right after I watched the Trash empty.

Excellent!